A pegmatite from Diethensdorf, Saxonian Granulite Massif, Germany, contains fine-grained aggregates of at least three different varieties of niobian rutile and a (W, Sc)-rich ferrocolumbite. In addition, rutile I occurs as larger grains. Electron microprobe analyses of niobian rutile gave compositions close to the general formula (Fe,Mn)(x)(Nb,Ta)(2x)Ti3-3xO6 with Nb and Fe contents decreasing in the order rutile I --> rutile 2 --> rutile 3 and Ti increasing accordingly. The substitution of (Ti,Sn) by Fe + (Nb,Ta) is 35-32 at% in rutile 1, 28-26 at% in rutile 2, and 24-19 at% in rutile 3. The intergrown ferrocolumbite has Ta/(Nb + Ta) ratios of <0.10 and Mn/(Fe + Mn) ratios <0.25, and shows unusually high contents Of Sc2O3 and WO3 (UP to 4.0 and 8.8 wt%, respectively). Powder Xray diffraction (XRD) analysis with Guinier and Bragg-Brentano methods identified at least three rutile phases (herein termed A, 13, and C) with cell volumes decreasing with the Nb (+ Ta, W) contents. Nb/Ti ratios of rutiles estimated from Rietveld refinements roughly conform to the results of electron microprobe analysis. The cation distribution in the ferrocolumbite was refined on the basis of a two-scatterer model at sites 8d and 4c in space group Pbcn, leading to ordering of the heavy atoms on site 8d. Textural evidence suggests that the fine-grained intergrowths of ferrocolumbite + rutile 2 + rutile 3 (+ rutile 1) were formed by exsolution from a precursor phase that most probably was not rutile 1.

Phases and phase transitions in three binary systems, Cu–Se, In–Se, Cu–In and in the ternary and quaternary systems Cu–In–Se (Ga) were investigated by in situ high energy powder diffraction in a temperature range from 25 to 550 °C. Results for the binary systems are compared to the known equilibrium phase diagrams of Cu–In, Cu–Se and In–Se. Above 225 °C Cu–In and Cu–Se follow the equilibrium phase diagrams. For In–Se significant deviations from the equilibrium diagram are observed. The results on binary systems yielded the basis for the qualitative phase analysis of the phase sequences observed in the CuInSe2 precursors during thermal anneal. On ternary and quaternary systems Cu–In–Se–(Ga) the reaction path to the formation of CuInSe2 could be determined in real time. Deviations of phase sequences from the equilibrium phase diagrams are attributed to the digression from the chemical rather than the thermal equilibrium. CuInSe2 finally crystallises from the direct precursors Cu2Se (Cu2−xSe, respectively) and InSe within a melt rich in selenium. The influence of gallium and sodium on the phase sequences and the resulting formation of CuInSe2 are discussed. Both, Na and Ga promote the crystallisation of Cu2Se, the direct precursor phase for CuInSe2. A comparison of the crystallographic structures of Cu2Se and InSe shows that epitaxial growth of InSe (0001) on Cu2Se (111) lattice planes is feasible. Based upon the experimental and crystallographic analysis a qualitative model for CuInSe2 crystallisation from the precursors in the melt is developed.

The status of our pilot process for Cu(In,Ga)(S,Se)2 (CIGSSe) thin films on 60×90 cm2 glass substrates is described. In a newly developed large area rapid thermal processing (RTP) furnace the CIGSSe layer is formed from sputtered metallic precursors coated by an evaporated Se film. We present device characteristics of pilot line modules and discuss material issues critical for up scaling of our lab process. We demonstrate that thin silicon nitride layers effectively impede the Na diffusion from the float glass. The accurate sodium dose required for high efficiency devices is deposited on the Mo layer. The Na content in the reacted CIGSSe film is affected by oxygen in the Mo. The loss of sodium can be eliminated choosing appropriate Mo sputtering conditions. Cu(Ga) and In can be sputtered in a multi (>200) layer sequence on a lab scale. In the pilot process, only a few alternating layers are deposited. The structural properties of both types of precursors and reacted CIGSSe films are investigated. Absorbers processed in the large area, pilot line RTP show good crystal quality, grain sizes and uniformity of composition. Maps of the photoluminescence decay rate are shown. Average lifetimes of 30 ns are obtained. Cell efficiencies up to 13.5% are obtained using pilot line precursor and large area RTP. The module process currently is being optimized. Best circuit efficiencies on 30×30 cm2 substrates are at 11% to date.

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